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Abstract:

Method of conversion of heat into fluid power includes pumping of the
working liquid into a hydropneumatic accumulator with gas compression,
subsequent gas expansion with displacement of the working liquid from the
other accumulator as well as supply of heat to the gas by transferring
the gas through the hotter heat exchanger and removal of heat from the
gas by transferring the gas through another, colder heat exchanger
performed so that the average temperature of the gas during expansion is
higher than that during compression, wherein the gas is transferred
between different accumulators through said heat exchangers.
The device for conversion of heat into fluid power includes at least two
accumulators, the means for liquid supply and intake as well as the means
for heating and cooling containing at least two flow-type gas heat
exchangers installed with the possibility of gas transfer through them
between gas reservoirs of different accumulators.
The efficiency and rate of heat conversion into fluid power are
increased. Reliability and high power density are ensured.

Claims:

1. A method of conversion of heat into fluid power including pumping of
the working liquid into the liquid reservoir of at least one of two or
more hydropneumatic accumulators (hereinafter the accumulator) with gas
compression in its gas reservoir, gas expansion in the gas reservoir of
at least one accumulator with displacement of the working liquid from its
liquid reservoir as well as supply of heat to the gas and removal of heat
from the gas performed so that the average temperature of the gas during
expansion is higher than that during compression, wherein heat is
supplied to the gas by transferring the gas through a hotter heat
exchanger while heat is removed from the gas by transferring the gas
through another, colder heat exchanger, while the gas is transferred
between the gas reservoirs of different accumulators through said heat
exchangers.

2. The method according to claim 1, wherein the walls of the gas
reservoir of at least one accumulator are maintained colder and the gas
is transferred into it through the colder heat exchanger while the walls
of the gas reservoir of another accumulator, at least one, are maintained
hotter and the gas is transferred into it through the hotter heat
exchanger.

3. The method according to claim 2, wherein the walls of the liquid
reservoir of at least one accumulator and the working liquid in it are
maintained colder and the walls of the liquid reservoir of another
accumulator, at least one, and the working liquid in it are maintained
hotter.

4. The method according to claim 3, wherein the working liquid displaced
from at least one accumulator is passed through a regenerating liquid
heat exchanger while during pumping of the working liquid into this
accumulator it is passed through the same regenerating liquid heat
exchanger in the opposite direction.

5. The method according to claim 3, wherein the hotter working liquid is
separated from the colder working liquid by at least one movable heat
insulator.

6. The method according to claim 3, wherein one working liquid is used in
colder liquid reservoir, another working liquid is used in hotter liquid
reservoir, while these different working liquids are separated by at
least one movable separator.

7. The method according to claim 2, wherein at least three accumulators
are used, while the walls of the gas reservoirs in at least two of them
are maintained colder and the gas is transferred between them with
compression through the colder heat exchanger.

8. The method according to claim 2, wherein at least three accumulators
are used, while the walls of the gas reservoirs in at least two of them
are maintained hotter and the gas is transferred between them with
expansion through the hotter heat exchanger.

9. The method according to claim 1, wherein the walls of the gas
reservoir in at least one accumulator are separated from the heated gas
flow by means of thermal protection.

10. The method according to claim 1, wherein forced gas convection is
created by a gas blower in the gas reservoir of at least one accumulator.

11. The method according to claim 10, wherein forced convection is
created by transferring the gas by means of the gas blower through at
least one heat exchanger with gas withdrawal from the gas reservoir of
said accumulator and return of the gas into the same gas reservoir.

12. The method according to claim 10, wherein the gas blower is driven by
a hydromotor that is driven by the liquid flowing between this
fluid-power motor and the liquid reservoir of at least one of said
accumulators.

13. The method according to claim 1, wherein the conversion is performed
in the cycle where at least at one stage heat is removed from the gas
with the gas cooling and at least at one stage heat is supplied to the
gas with the gas heating, while heat is removed from it at the stage with
gas cooling to a regenerating heat exchanger and then the removed heat is
supplied to the gas from the regenerating heat exchanger at the stage
with gas heating.

14. The method according to claim 13, wherein the hot heat-transfer
medium is used as a heat source and a counter-flow hot heat exchanger is
used through which the gas is transferred during heat supply so that heat
is supplied to the gas entering the heat exchanger from the heat-transfer
medium leaving the heat exchanger while the heat is supplied to the gas
leaving the heat exchanger from the heat-transfer medium entering the
heat exchanger, while at least part of this counter-flow hot heat
exchanger is used as a regenerating heat exchanger by transferring the
gas through this part during cooling in one direction and during heating
in the reverse direction.

15. The method according to claim 1, wherein the gas is transferred
between the gas reservoirs by pumping the liquid into the liquid
reservoir of at least one of these accumulators and displacing the liquid
from the liquid reservoir of at least one more accumulator, with a liquid
flow created between the liquid reservoirs of these accumulators so that
the pressure difference between any parts of the liquid in this flow does
not exceed 30% of the pressure of the liquid in the liquid reservoir into
which it is pumped, preferably this difference does not exceed 5% of said
pressure.

16. The method according to claim 15, wherein said liquid flow is created
by means of a hydraulic transformer having at least three liquid ports,
with two of them connected to the liquid ports of the accumulators,
between which said liquid flow is created, while said transformer is
driven by another liquid flow flowing through its at least one more port.

17. The method according to claim 15, wherein at least one accumulator is
used including at least two liquid reservoirs, separated from the gas
reservoir by one common piston separator, while said flow of the working
liquid is created by maintaining the pressure of the liquid in at least
one liquid reservoir of this accumulator higher than the gas pressure in
the gas reservoir of the same accumulator, whereas maintaining the
pressure of the liquid in at least one other liquid reservoir of this
accumulator less than said gas pressure.

18. The method according to claim 16, wherein for pumping and
displacement of the working liquid means for liquid supply and intake are
used including the line with the first pressure and the line with the
second pressure that is higher than the first one while conversion is
performed in a cycle including: the stage of gas compression in the
accumulator with the colder gas reservoir during pumping of the working
liquid into its liquid reservoir from the hydraulic transformer also
connected to the lines with the first and second pressures; the stage of
gas transfer from the accumulator with the colder gas reservoir through
the hotter heat exchanger into the accumulator with the hotter gas
reservoir at the working liquid pressure in the accumulators higher than
the second pressure, with creation of the working liquid flow from the
liquid reservoir of the accumulator with the hotter gas reservoir to the
line with the second pressure, with this flow driving the hydraulic
transformer that creates the working liquid flow from the accumulator
with the hotter gas reservoir to the accumulator with the colder gas
reservoir; the stage of gas expansion in the accumulator with the hotter
gas reservoir with displacement of the working liquid from its liquid
reservoir into the hydraulic transformer also connected to the lines with
the first and second pressures as well as the stage of the gas transfer
from the accumulator with the hotter gas reservoir through the colder
heat exchanger into the accumulator with the colder gas reservoir at the
working liquid pressure in the accumulators lower than the first
pressure, with creation of the working liquid flow from the line with the
first pressure to the liquid reservoir of the accumulator with the hotter
gas reservoir, while this flow drives the hydraulic transformer creating
the working liquid flow from the accumulator with the colder gas
reservoir to the accumulator with the hotter gas reservoir.

19. The method according to claim 18, wherein the fluid power obtained
during heat conversion is transferred to a load through the hydraulic
transformer, its two ports being connected to said lines with the first
and second pressures and two other ports being connected to the lines
with high and low output pressures.

20. A device for conversion heat into fluid power including at least two
hydropneumatic accumulator, where the liquid reservoir in each of them
communicating with the means for liquid supply and intake is separated by
a movable separator from the gas reservoir communicating with the means
of heating and cooling made with the possibility of heating and cooling
the inflowing gas wherein the means of heating and cooling contain at
least two gas heat exchangers installed with the possibility of
transferring gas through them between the gas reservoirs of different
accumulators, while the means of heating and cooling are made with the
possibility of maintaining at least one of these heat exchangers colder
and maintaining at least one more heat exchanger hotter.

21. The device according to claim 20, wherein the means of heating and
cooling are made with the possibility of maintaining the walls of the gas
reservoir of at least one accumulator colder and transferring gas into it
through the colder heat exchanger while maintaining the walls of the gas
reservoir of another accumulator, at least one, hotter and transferring
gas into it through the hotter heat exchanger.

22. The device according to claim 21, wherein the means of heating and
cooling are made with the possibility of maintaining the walls of the
liquid reservoir of at least one accumulator and the working liquid in it
colder while maintaining the walls of the liquid reservoir of another
accumulator, at least one, and the working liquid in it hotter.

23. The device according to claim 21, wherein the means for liquid supply
and intake include at least one liquid regenerating heat exchanger
connected with the liquid reservoir of at least one accumulator and made
with the possibility of removing heat from the liquid during its
displacement through it from this accumulator and supplying the removed
heat to the liquid during its pumping through it back into this
accumulator.

24. The device according to claim 21, wherein the means for liquid supply
and intake include at least one liquid buffer including two liquid
reservoirs separated by a movable heat insulator.

25. The device according to claim 21, wherein the means for liquid supply
and intake include at least one liquid buffer including two liquid
reservoirs separated by a movable separator.

26. The device according to claim 21, wherein it includes at least three
accumulators while the means of heating and cooling are made with the
possibility of maintaining the walls of the gas reservoirs of at least
two accumulators colder and transferring the gas between them through the
colder gas heat exchanger.

27. The device according to claim 21, wherein it includes at least three
accumulators while the means of heating and cooling are made with the
possibility of maintaining the walls of the gas reservoirs of at least
two accumulators hotter and transferring the gas between them through the
hotter gas heat exchanger.

28. The device according to claim 20, wherein at least one accumulator is
provided with means of thermal protection made with the possibility of
separating the walls of the gas reservoir of the accumulator from the
input gas flow.

29. The device according to claim 20, wherein the means of heating and
cooling include at least one gas blower installed with the possibility of
creating forced gas convection in the gas reservoir of at least one
accumulator.

30. The device according to claim 29, wherein the gas reservoir of at
least one accumulator communicates with the means of heating and cooling
through at least two gas lines with the possibility of withdrawing the
gas from said gas reservoir through one of said gas lines by the gas
blower, transferring the withdrawn gas at least through one gas heat
exchanger and returning the gas to the same gas reservoir through another
gas line.

31. The device according to claim 29, wherein the means for liquid supply
and intake include at least one hydromotor cinematically connected with
at least one gas blower, while the hydromotor is installed with the
possibility of being driven by the liquid flow between it and the liquid
reservoir of at least one accumulator.

32. The device according to claim 20, wherein at least one gas heat
exchanger is made with the possibility of removing heat from the gas at
transferring the gas through it in one direction and supplying the heat
removed from it at transferring the gas through it in the opposite
direction.

33. The device according to claim 20, wherein at least one gas heat
exchanger has channels made for passing an external heat transfer medium
with the possibility of supplying heat from this heat transfer medium to
the gas so that the heat is supplied to the gas entering the heat
exchanger from the external heat transfer medium leaving the heat
exchanger while the heat to the gas leaving the heat exchanger is
supplied from the external heat transfer medium entering the heat
exchanger, while said heat exchanger has at least one additional gas port
and the means of heating and cooling contain at least one channel
connecting the additional gas port with the gas reservoir of at least one
accumulator and are made with the possibility of locking this channel.

34. The device according to claim 20, wherein the means for liquid supply
and intake include the means of inter-accumulator transfer of liquid made
with the possibility of creating a flow of liquid between the liquid
reservoirs of at least two accumulators so that the pressure difference
between any parts of liquid in this flow does not exceed 30% of the
pressure of the liquid in the liquid reservoir into which it is pumped,
preferably this difference does not exceed 5% of said pressure.

35. The device according to claim 34, wherein the means of
inter-accumulator transfer of liquid include at least one hydraulic
transformer with at least three liquid ports that is installed with the
possibility of communicating by its two ports with the liquid reservoirs
of at least two accumulators and creating a flow of liquid between them
when the liquid flows through its other port, at least one.

36. The device according to claim 34, wherein at least one accumulator
includes at least two liquid reservoirs separated from one gas reservoir
by one common piston separator, while the means of inter-accumulator
transfer of liquid are made with the possibility of creating flow of
liquid between at least one liquid reservoir of this accumulator and at
least one liquid reservoir of another accumulator.

37. The device according to claim 34, wherein the means of liquid supply
and intake contain the first and second lines with the possibility of
maintaining the first and second pressures in them, respectively, as well
as the hydraulic transformer with at least three ports installed with the
possibility of connecting with said two lines and liquid exchange with
the liquid reservoir of at least one accumulator at the pressures
different from the pressures in said lines.

38. The device according to claim 37, wherein the means for liquid supply
and intake include the hydraulic transformer with at least four ports
installed with the possibility of connecting two ports with said first
and second lines and two other ports with two output lines and of
maintaining the pressures in the output lines different from said
pressures in the first and second lines.

Description:

[0001] The invention refers to mechanical engineering and can be used for
effective conversion of heat from various sources, including the sun,
internal or external combustion engines, high-temperature fuel cells,
geothermal sources, etc. into fluid power.

STATE OF THE ART

[0002] There is a method of conversion heat into fluid power implemented
in the device disclosed in U.S. Pat. No. 557,964. The method includes
pumping the working liquid into a hydropneumatic accumulator (hereinafter
the accumulator) with gas compression, gas expansion with displacement of
the liquid from the accumulator as well as heat supply to the gas and
heat removal from the gas performed so that the average gas temperature
during expansion should be higher than that during compression.

[0003] The method has been implemented by means of the device including at
least two hydropneumatic accumulators (named "the first and the second
liquid tanks" by the authors). In each accumulator the liquid reservoir
communicating with the means for supply and intake of the liquid is
separated by a movable separator from the gas reservoir communicating
with the means of heating and cooling made with the possibility of
heating and cooling the incoming gas. The heating and cooling means
include gas receivers (named "the first and the second gas vessels" by
the authors), each of them communicating with the gas reservoir of the
respective (first or second) accumulator, as well as means of gas heating
and cooling in the receivers (named, respectively, "the first and the
second means of heating and cooling" by the authors) and a control system
made with the possibility of alternating gas cooling and heating in the
receivers. The means for supply and intake of the liquid include a
hydraulic pump and a hydraulic motor as well as valves.

[0004] Heat is supplied to the gas in the receiver from the hot heat
transfer medium through the walls of the heating heat exchanger which is
placed either outside the receiver and transfers heat to the gas through
the walls of the receiver or is placed inside the receiver transferring
heat to the gas through its own strong walls. It is proposed to use
exhaust gases of internal combustion engines, for example, as the hot
heat transfer medium.

[0005] Heat from the gas in the receiver is extracted to the external
cooling heat transfer medium either directly through the walls of the
receiver or through the strong walls of a separate cooling heat exchanger
placed inside the receiver. It is proposed to use the ambient air or
water as a cooling heat transfer medium.

[0006] The switching from heat supply to heat removal and back is effected
by turning off the flow of the hot heat transfer medium and turning on
the flow of the cooling heat transfer medium and vice versa using the
valves.

[0007] Each accumulator with its receiver and the means of heating and
cooling is a separate converter of heat into fluid power. Gas reservoirs
of different accumulators do not communicate while liquid reservoirs are
connected to the means for supply and intake of the liquid via separate
valves. To reduce pulsations of input and output flows in said device two
and more converters of this kind are used so that pumping of liquid into
the accumulator of one converter should correspond to displacement of
liquid from the accumulator of the other converter.

[0008] In each converter of this kind the aforesaid method is implemented
as a cyclic process including four consecutive stages: [0009] pumping
of the working liquid from the means for supply and intake of the liquid
into the accumulator with gas compression and its displacement from the
accumulator into the receiver and with removal of heat from the gas in
the receiver to the external cooling heat transfer medium, [0010]
isochoric heating of the gas in the receiver by supplying heat from the
hot heat transfer medium, for example, to it, [0011] gas expansion with
its displacement from the receiver into the accumulator, with
displacement of the liquid from the accumulator into the means for supply
and intake of the liquid and with continued supply of heat to the gas in
the receiver from the hot heat transfer medium, for example, [0012]
isochoric cooling of the gas by removing heat from the gas in the
receiver to the external cooling heat transfer medium.

[0013] Due to supply of heat to the gas at the stages of isochoric heating
and subsequent expansion as well as heat removal from the gas at the
stages of isochoric cooling and subsequent compression, the average
temperature (and, consequently, the average pressure) of the gas during
expansion is higher than during compression; therefore, the gas expansion
work exceeds the gas compression work. As a result, some part of the heat
is converted into additional fluid power.

[0014] However, cyclic heating and cooling of the gas occurs in the same
volume of the gas receiver, which implies cyclic heating and cooling not
only the gas but also heat exchangers as well as the walls of the
receiver. There is heat exchange between the gas at high pressure
(hundreds of bars) and heat-exchange media at low pressure (down to units
of bars for exhaust gases). Heat exchangers of relevant strength as well
as the walls of the receiver are massive and their thermal capacity is
considerably (at least dozens of times) higher than the thermal capacity
of the gas in the receiver. Their thermal capacity is much higher
(hundreds and thousands of times) than thermal capacity of atmospheric
air and exhaust gases pumped through heat exchangers per second.

[0015] As a result, thermal inertia of the device is high while the gas
cooling and heating rates are low, which reduces the speed of operation
and the average power density of the device and is the first substantial
shortcoming of the proposed solution. Gas heating and cooling in the
receiver occurs due to the gas heat conductivity and natural convection,
which also reduces the heating and cooling speeds and related specific
power.

[0016] In this case most heat of the external source is spent on heating
massive heat exchangers and walls of the receiver cooled at the previous
stages of the cycle rather than on conversion into fluid power. Upon
completion of the gas expansion the heat accumulated in the heat
exchanger is transferred to the cooling heat transfer medium and
released. Therefore, the heat utilization efficiency appears to be low,
which is the second and most essential shortcoming of the proposed
solution. The use of the heat removed from one of the receivers during
its cooling to heat another receiver proposed by the authors allows
decreasing heat losses by not more than 50%.

[0017] Additional heat losses occur when the flow of heated gas enters the
accumulator where it blows over the walls of the gas reservoir of the
accumulator and gives heat to them fast.

[0018] It should be also noted that in the proposed solution increasing
the thermodynamic efficiency of the gas cycle is principally incompatible
with increasing the general efficiency of conversion of the heat of an
external source into fluid power. Striving to increase the gas cycle
efficiency the authors suggest heating the gas in the receiver until the
gas temperature in the receiver approaches the temperature of the hot
heat transfer medium. It is similarly proposed to cool the gas in the
receiver until its temperature equals the temperature of the ambient air
or another cooling heat transfer medium. However, as the temperature of
the heat exchanger approaches the temperature of the hot heat transfer
medium the part of the heat removed from the heat transfer medium to the
heat exchanger tends towards zero. Thus, despite the growing
thermodynamic efficiency of the gas cycle the efficiency of conversion of
the heat of the external source into fluid power drops even lower. The
speed and average power drop as well because the process of temperature
equalization in the receiver is asymptotic.

[0019] Cyclic heating and cooling of the body of the receiver and heat
exchangers under high pressure accelerates their fatigue breakdown and
decreases the reliability and safety of the proposed device. Besides, the
need to switch the flow of the hot heat transfer medium by means of the
valves reduces the reliability of the device, especially at the use of
internal combustion engine exhaust gases combining high temperature (to
800-900° C.) and chemical aggressiveness. A failure of the valve
switching the exhaust gas flow may result either in dangerous
uncontrolled overheating of the gas in the receiver with increased
pressure over the maximum permissible level or to a failure of the
internal combustion engine in case of a blocked exhaust duct.

[0020] Thus, the low efficiency and rate of heat conversion into fluid
power, low specific power and low reliability are the major shortcomings
of the proposed solution. Another essential shortcoming of the proposed
solution is the impossibility of accumulating heat and generating fluid
power during temporary shutdown or flow reduction of the hot
heat-transfer medium.

ESSENCE OF THE INVENTION

[0021] The objective of the present invention is to increase the
efficiency and speed of conversion of heat into fluid power.

[0022] Another objective of the present invention is to increase power
density and reliability of the device converting heat into fluid power.

[0023] Another objective of the present invention is to ensure the
possibility of heat storage and conversion into fluid power during
temporary shutdown or reduction of the heat supply power.

METHOD

[0024] The method of heat conversion into fluid power proposed for
achieving this objectives includes pumping of the working liquid into the
fluid reservoir of at least one hydropneumatic accumulator (hereinafter
the accumulator) with gas compression in its gas reservoir as well as gas
expansion in the gas reservoir of at least one accumulator with
displacement of the fluid from its fluid reservoir as well as heat supply
to the gas and heat removal from the gas performed so that the average
gas temperature during expansion is higher than that during compression.

[0025] The objective is achieved by ensuring that heat is supplied to the
gas by transferring the gas through a hotter heat exchanger and heat is
removed from the gas by transferring the gas through another, colder heat
exchanger, with at least two accumulators being used and with the gas
being transferred between different accumulator through said heat
exchangers.

[0026] To maintain the heat exchanger hotter it is brought into a thermal
contact with the heat source (by means of heat conductivity, radiation or
heat transfer by the flow of the heating heat-transfer medium). To
maintain the heat exchanger colder it is brought into a thermal contact
with the cooling heat-transfer medium. Due to the fact that the average
gas temperature during expansion is higher (and, hence, the average gas
pressure is higher as well) than that during compression the gas
expansion work exceeds the gas compression work. As a result, some part
of the heat carried from the heat source to the cooling heat-transfer
medium via the heat exchangers and the gas flow is converted into
additional fluid power that can be used to perform mechanical work. For
pumping the working liquid and to use the additional fluid power obtained
at displacement of the liquid by the hotter gas means of supply and
intake of liquid are used that may include hydraulic pumps and motors or
hydraulic pressure transformers (hereinafter hydraulic transformers).

[0027] Due to the gas transfer via heat exchangers between different
accumulators it is the transferred gas only rather than the massive heat
exchangers that is subject to cyclic heating and cooling. This results in
much lower heat losses and increased efficiency of heat conversion into
fluid power.

[0028] Forced convection of the gas flowing through the heat exchangers
ensures its high heating and cooling rate, which allows conversion of the
heat of an external source into fluid power at a high rate and specific
power.

[0029] Elimination of cyclic heating and cooling of the heat exchangers
and other elements of the heating and cooling means being under high
pressure increases their reliability and safety of heat conversion into
fluid power.

[0030] The heat accumulated in the hotter heat exchanger is not released
and can be used for conversion into fluid power during temporary shutdown
or reduction of the power of the external heat source.

[0031] To reduce heat losses when the walls of the gas reservoir of the
accumulator are blown over by the flow of the heated or cooled gas, the
walls of the gas reservoir of at least one accumulator are maintained
colder and the gas is transferred into it through the colder heat
exchanger while the walls of the gas reservoir of another accumulator are
maintained hotter and the gas is transferred into it through the hotter
heat exchanger.

[0032] To reduce gas heat losses through the accumulator separator caused
by the temperature difference of the gas and liquid in the accumulator,
the walls of the liquid reservoir of at least one accumulator and the
working liquid in it are maintained colder while the walls of the liquid
reservoir of at least one other accumulator and the working liquid in it
are maintained hotter.

[0033] To prevent heat losses with working liquid flows the invention
provides for both heat insulation of the flows and heat regeneration when
the hotter (or colder) working liquid is pumped and displaced.

[0034] For heat regeneration the working liquid displaced out of at least
one accumulator is passed through the regenerating liquid heat exchanger.
When the working liquid is pumped into this accumulator, it is passed
through the same regenerating liquid heat exchanger in the opposite
direction.

[0035] For heat insulation of the liquid flows the hotter working liquid
is separated from the colder working liquid by at least one movable heat
insulator.

[0036] For operation with increased difference of temperatures between the
accumulators one working liquid is used in the colder liquid reservoir
while another working liquid is used in the hotter liquid reservoir,
these two different working liquids being separated by at least one
movable separator. This movable separator may also be a movable heat
insulator: for example, a piston made of a low heat conductivity material
(polymer or ceramic) or an elastic separator coated with open-cell foamed
elastomer.

[0037] The use of a high-temperature organic (based on diphenyl or
diphenyloxide for example) or silicon-organic (based on dimethylsiloxane
for example) working liquid allows to maintain the temperature of the
hotter accumulator and the working liquid in it at 300-400 C. The use of
an inorganic working liquid (molten tin or other metal, for example)
allows raising the maximum temperature higher up to the temperature
stress limit of the material of the accumulator walls.

[0038] The increased temperature of the hotter accumulator and the working
liquid in it increase the efficiency of conversion heat into fluid power,
especially when heat losses with liquid flows are eliminated in the
aforesaid ways.

[0039] The stable temperature condition of the strong shells of the
accumulators under high pressure also increases their reliability and
safety of heat conversion into fluid power. For the gas compression
process to approach the isothermal one, at least three accumulators are
used, with the walls of the gas reservoirs in at least two of them being
maintained colder and the gas being transferred between them with
compression through the colder heat exchanger.

[0040] For the gas expansion process to approach the isothermal one, at
least three accumulators are used, with the walls of the gas reservoirs
in at least two of them being maintained hotter and the gas being
transferred between them with expansion through the hotter heat
exchanger.

[0041] To increase the maximal gas temperature above the maximal
permissible temperature of the working liquid or separator in at least
one accumulator the walls of the gas reservoir are separated from the
heated gas flow by means of thermal protection.

[0042] To bring the processes of gas compression or expansion closer to
the isothermal ones and further increase of efficiency of heat conversion
into fluid power in the gas reservoir of at least one accumulator a
forced gas convection is created using a gas circulating pump
(hereinafter referred to as a gas blower for brevity).

[0043] Both external gas blowers and gas blowers embodied inside the
accumulator (in its housing or in the gas reservoir) are used.

[0044] For a better approach to isothermality the forced convection is
created by transferring the gas by means of the gas blower through at
least one heat exchanger with gas withdrawal from the gas reservoir of at
least one accumulator and gas return to the same gas reservoir. It is
preferred that to reduce heating and cooling losses in the gas lines the
gas from this gas reservoir should be withdrawn through one gas line and
returned through another gas line.

[0045] The gas blower can be actuated by electric, hydraulic or other
motors via the shaft or another kinematic link of the drive provided with
seals preventing compressed gas leakages. To reduce leakage and friction
losses in the seals the kinematic links of the gas blower drive it is
actuated by a hydromotor working at close pressures of the liquid
(preferably differing from the gas pressure in the gas blower by not more
than several bars). It is preferred that the hydromotor should be
actuated by the liquid flowing between this hydromotor and the liquid
reservoir of at least one of said accumulators when liquid is pumped into
it or is displaced out of it through this hydromotor.

[0046] To increase the thermodynamic efficiency, especially when
compression or expansion are close to the isothermal ones, conversion is
effected as a cycle with gas heat regeneration when at least at one stage
heat is removed from gas with gas cooling and at least at one stage heat
is supplied to the gas with gas heating, while some part of the heat
removed from the gas at the cooling stage is used for supply to the gas
at the heating stage. For that purpose heat is removed from the gas at
the cooling stage to the regenerating heat exchanger and heat is supplied
to the gas at the heating stage first from the regenerating heat
exchanger and then from the external source of heat.

[0047] When using the heat effectively given away by the source at high
temperature, a high-temperature fuel cell, for example, as well as heat
of the sun or another source of radiant energy, the use of a separate
regenerating heat exchanger is preferred. At the gas cooling stage gas is
passed first through the separate regenerating heat exchanger in the
cooling direction and then through the colder heat exchanger while at the
gas heating stage it is passed first through the regenerating heat
exchanger in the heating direction, preferably opposite to the cooling
direction, and then through the hotter heat exchanger.

[0048] When heat is transferred from the source by means of a hot heat
transfer medium released after heat removal (exhaust gases, for example)
a counterflow hotter heat exchanger is used to increase the efficiency.
Gas is transferred through it during heat supply in the direction
opposite to the direction of the hot heat transfer medium flow so that
heat is supplied to the gas entering the heat exchanger from the heat
transfer medium leaving the heat exchanger while heat is supplied to the
gas leaving the heat exchanger from the heat transfer medium entering the
heat exchanger. This ensures both higher gas heating rate and the cooling
rate of the hot heat transfer medium (for example, outgoing flows of end
products of fuel combustion or water steam). It is preferred that this
very counterflow heat exchanger (or part of it) should be used as the
regenerating heat exchanger, with gas passed through it (or part of it)
in one direction during cooling and in the opposite direction during
heating.

[0049] At the increased degree of heat regeneration the gas cycles
including two isotherms and two isobars (or two other stages equidistant
in "temperature-entropy" coordinates, for example, two isochors) approach
the generalized Carnot cycles that allow heat conversion into gas work at
the maximal thermodynamic efficiency.

[0050] To reduce hydromechanical losses the part of the liquid exposed to
considerable pressure changes during transfer through the hydromechanical
devices is reduced. For that purpose gas is transferred between the gas
reservoirs of the accumulator pumping liquid into the liquid reservoir of
at least one accumulator and displacing liquid from the liquid reservoir
of at least one other accumulator. A liquid flow is created between the
liquid reservoirs of these accumulators so that the pressure difference
between any parts of the liquid in this flow does not exceed 30% of the
liquid pressure in the liquid reservoir in which it is pumped to; it is
preferred that this difference should not exceed 5% of said pressure.

[0051] In conventional accumulators each gas reservoir corresponds to one
liquid reservoir, their pressure differing by a small value only related
to friction at the piston separator travel or to deformation of the
elastic separator. Said liquid flow between these accumulators is created
by hydromechanical means of inter-accumulator liquid transfer (a liquid
pump or a hydraulic transformer, for example) overpowering the pressure
difference between the liquid reservoirs of the accumulators, the gas
reservoirs of which communicate via heat exchangers.

[0052] Said pressure difference between different parts of the liquid flow
passing between the liquid reservoirs of the accumulators with the gas
reservoirs communicating via heat exchangers is determined by the
resistance of the heat exchangers; communication lines (gas and liquid
ones) as well as by the efficiency of hydromechanical means of
inter-accumulator liquid transfer. Compared to the total pressure of the
liquid in the accumulator this pressure difference is small (preferably
does not exceed several bars). Therefore, the losses related to leakages
and friction in the hydromechanical means of inter-accumulator liquid
transfer are also small.

[0053] Said hydromechanical means may include a fluid pump actuated by
electric, hydraulic or other motor via the shaft or another kinematic
link of the drive provided with seals preventing liquid leakages. To
reduce losses of leakages and friction in the seals this liquid flow
between the accumulators is preferably created by means of the hydraulic
transformer having at least three liquid ports. For creating
inter-accumulator liquid flow its two ports are connected with liquid
ports of the respective accumulators and it is actuated by another flow
of liquid flowing through its at least one other port. It is preferred
that this other flow should be the differential one between the flow
entering the hydraulic transformer from the accumulator (accumulators),
from which the incoming gas displaces the liquid, and the flow leaving
the hydraulic transformer into the accumulator (accumulators), in which
the incoming liquid displaces the gas.

[0054] It is implied that different hydraulic transformers both with
separate kinematically interconnected pumps and hydromotors (both rotor
and linear ones) and integrated ones, for example, phase-regulated
hydraulic transformers, with every cylinder working as a motor during one
part of the revolution and as a pump during the other part, can be used.

[0055] In terms of compactness it is preferable to use at least one
accumulator that combines the functions of hydropneumatic accumulator and
hydraulic transformer. Such an accumulator includes at least two liquid
reservoirs separated by one common piston separator from one gas
reservoir. These liquid reservoirs have independent liquid ports and are
separated from each another, which allows maintaining different pressures
in them so that the total pressure force of the liquid on the separator
balances the force of gas pressure on the separator. For the creation of
the aforesaid inter-accumulator flow of liquid the pressure of the liquid
in at least one liquid reservoir of this accumulator is maintained above
the gas pressure in the gas reservoir of this very accumulator, whereas
the pressure of the liquid in at least one other liquid reservoir of this
accumulator is maintained below said gas pressure. At least one of these
liquid reservoirs connected with the liquid reservoir of at least one
other accumulator participates in said inter-accumulator liquid flow
while at least one other liquid reservoir of the same accumulator is used
to maintain the proportion of liquid pressures in accordance with the gas
transfer direction. The pressure in the liquid reservoir participating in
the inter-accumulator liquid transfer is raised or reduced relative to
the gas pressure by the value sufficient for creation of a liquid flow.
For that purpose the pressure in the liquid reservoir not involved in the
inter-accumulator liquid transfer is reduced or raised accordingly by the
value necessary to keep the balance of the pressure forces on the piston
separator. When gas is transferred to the gas reservoir of this
accumulator, the said liquid flow is created to another accumulator from
at least one of the liquid reservoirs of this accumulator maintaining the
pressure in this liquid reservoir higher than the gas pressure in this
gas reservoir while the pressure in at least one other liquid reservoir
of the same accumulator is maintained less than said gas pressure. When
gas is transferred from the gas reservoir of this accumulator, the said
liquid flow is created from another accumulator to at least one of the
liquid reservoirs of this accumulator maintaining the pressure in this
liquid reservoir less than the gas pressure in this gas reservoir while
the pressure in at least one other liquid reservoir of the same
accumulator is maintained higher than said gas pressure.

[0056] The invention provides that the liquid flow is created through the
hydraulic transformer and the necessary valves both directly between the
liquid reservoirs of different accumulators and through an intermediate
liquid buffer moving its movable separator or heat insulator.

[0057] For further reduction of hydromechanical losses the intake of
displaced working liquid and its pumping are effected by means for supply
and intake of liquid including a line with the first pressure and a line
with the second pressure. Both the first and the second pressures are
maintained high (preferably, dozens or hundreds of bars), with the second
pressure being higher than the first one. Conversion is effected as the
cycle including the stage of gas compression in the accumulator with the
colder gas reservoir, the stage of gas transfer from it through the
hotter heat exchanger into the accumulator with the hotter gas reservoir,
the stage of gas expansion in the accumulator with the hotter gas
reservoir as well as the stage of gas transfer from it through the colder
heat exchanger into the accumulator with the colder gas reservoir.

[0058] The gas from the accumulator with the hotter gas reservoir is
transferred into the accumulator with the colder gas reservoir at the
working liquid pressure in the accumulator being less than the first
pressure. The working liquid flow from the line with the first pressure
to the liquid reservoir of the accumulator with the hotter gas reservoir
is directed through the aforesaid hydraulic transformer that creates the
above-described working liquid flow from the accumulator with the colder
gas reservoir to the accumulator with the hotter gas reservoir.

[0059] The gas from the accumulator with the colder gas reservoir is
transferred into the accumulator with the hotter gas reservoir at the
working liquid pressure in the accumulators being higher than the second
pressure. The working liquid flow from the liquid reservoir of the
accumulator with the hotter gas reservoir to the line with the second
pressure is directed through the aforesaid hydraulic transformer that
creates the above-described working liquid flow from the accumulator with
the hotter gas reservoir to the accumulator with the colder gas
reservoir.

[0060] The gas in the accumulator (at least one) with the colder gas
reservoir is compressed by pumping the working liquid into its liquid
reservoir from the hydraulic transformer that is also connected to the
lines with the first and second pressures. This hydraulic transformer is
actuated by directing the liquid flow through it from the line with the
second pressure. During gas compression the pressure of the liquid pumped
from the hydraulic transformer into said liquid reservoir is raised by
raising the ratio between the volumetric flow rate of the liquid flowing
from the second line to the hydraulic transformer and the volumetric flow
rate of the liquid flowing from the hydraulic transformer to said liquid
reservoir.

[0061] The gas expansion in the accumulator (at least one) with the hotter
gas reservoir is actuated by creation of the working liquid flow
displacing from its liquid reservoir to the hydraulic transformer that is
connected also to the lines with the first and second pressures. This
flow actuates the hydraulic transformer with creation of the working
liquid flow from it to the line with the second pressure. During gas
expansion the pressure of the liquid displaced from said liquid reservoir
into the hydraulic transformer is reduced by decreasing the ratio between
the volumetric flow rate of the liquid flowing from the hydraulic
transformer to the second line and the volumetric flow rate of the liquid
flowing from said liquid reservoir to the hydraulic transformer.

[0062] Thus, as a result of every conversion cycle some part of the
working liquid is transferred from the line with the first pressure to
the line with the second, higher pressure. The sliding seals of the
hydraulic transformers work under differential pressures rather than full
pressures, which reduces the losses on leakages and friction.

[0063] The fluid power received by the aforesaid transfer of the liquid to
the line with the second pressure can be used in the load connected
between said lines with the first and second pressures. To extend the
possibilities of using the obtained fluid power it is proposed to use the
hydraulic transformer, its two ports being connected to said lines with
the first and second pressures and two other ports being connected to the
lines with the high and low output pressures. Thus, pressure decoupling
is effected optimizing the efficiency of the gas cycle by choosing said
first and second pressures in the lines and optimizing the load regime by
choosing the high and low output pressures.

Device

[0064] The above-described method is proposed to be implemented by the
device of conversion of the heat of an external source into fluid power
including at least two hydropneumatic accumulators, wherein the liquid
reservoir of each of them communicating with the means for supply and
intake of liquid is separated by a movable separator from the gas
reservoir communicating with the means of heating and cooling made with
the possibility of heating and cooling of the inflowing gas.

[0065] The means of heating and cooling contain at least two gas heat
exchangers installed with the possibility of gas transfer through them
between gas reservoirs of different accumulators, while the means of
heating and cooling are made with the possibility of maintaining at least
one of the heat exchangers colder and at least one other heat exchanger
hotter.

[0066] At least one heat exchanger is made with the possibility of
supplying heat to the gas from an external heat source. At least one
other heat exchanger is made with the possibility of removing heat from
the gas to the cooling heat transfer medium. Hereinafter in the
description of the working device the heat exchanger of the first type is
called the hotter heat exchanger while the heat exchanger of the second
type is called the colder heat exchanger. The heat exchanger made with
the possibility of removing heat from the gas and supplying the removed
heat to the gas is called the regenerating heat exchanger in similar
cases.

[0067] To eliminate heat losses of cyclic heating and cooling of the walls
of the gas reservoirs of the accumulators an embodiment is proposed in
which the means of heating and cooling are made with the possibility of
maintaining the walls of the gas reservoir of at least one accumulator
colder and transferring gas into it through the colder heat exchanger
while maintaining the walls of the gas reservoir of at least one other
accumulator hotter and transferring gas into it through the hotter heat
exchanger.

[0068] To eliminate heat losses through separators an embodiment is
proposed in which the means of heating and cooling are made with the
possibility of maintaining the walls of the liquid reservoir of at least
one accumulator and the working liquid in it colder while maintaining the
walls of the liquid reservoir of at least one other accumulator and the
working liquid in it hotter.

[0069] To implement the method with regeneration of the working liquid
heat the means for supply and intake of liquid include at least one
liquid regenerating heat exchanger. It is connected with the liquid
reservoir of at least one accumulator and is made with the possibility of
removing heat from the liquid during its displacement through it from
this accumulator and supplying the removed heat to the liquid during its
pumping through it into the accumulator.

[0070] To implement the method with heat insulation of the hotter part of
the working liquid from the colder one the means for supply and intake of
liquid include at least one liquid buffer including two liquid reservoirs
separated by a movable heat insulator.

[0071] To implement the method using different working liquids in
different accumulators the means for supply and intake of liquid include
at least one liquid buffer including two variable-volume reservoirs
separated by a movable separator.

[0072] Each liquid reservoir of the aforementioned liquid buffers is
installed with the possibility of communicating with the liquid reservoir
of at least one accumulator.

[0073] To reduce the mass and dimensions of the device and the aggregate
internal volume of the gas communication lines at least one gas heat
exchanger is made in the housing of the accumulator, for example, as a
gas port of this accumulator with the possibility of supplying heat to
the gas or removing heat from the gas (preferably as a gas port with
increased ratio between the area of the gas contacting surface and the
volume). Due to elimination of two intermediate ports and the gas line
the gas-dynamic losses during gas transfer through this heat exchanger
are also reduced.

[0074] To implement the method with approaching the gas compression
process closer to the isothermal one the embodiment of the device is
proposed including at least three accumulators while the means of heating
and cooling are made with the possibility of maintaining the walls of gas
reservoirs of at least two of the accumulators colder and gas transfer
between them through the colder gas heat exchanger.

[0075] To implement the method with approaching the gas expansion process
closer to the isothermal one an embodiment of the device is proposed
including at least three accumulators while the means of heating and
cooling are made with the possibility of maintaining the walls of the gas
reservoirs of at least two accumulators hotter and gas transfer between
them through the hotter gas heat exchanger.

[0076] To reduce heat losses at least one accumulator is provided with
thermal protection means made with the possibility of separating the
walls of the gas reservoir from the incoming gas flow.

[0077] When gas is heated to less than 150-200 C, to reduce the losses of
the separator friction and the cost said accumulator is made with an
elastic separator while the means of thermal protection include a
flexible porous heat insulator connected with the elastic separator.

[0078] When gas is heated to higher temperatures, said accumulator is
preferably made with a piston separator while the means of thermal
protection include a variable-length thermal screen installed along the
side cylindrical walls of the gas reservoir of the accumulator as well as
thermal screens installed opposite the separator and the gas reservoir
bottom. For temperature above 300 C the said thermal screens are
preferably made of metal while for lower temperatures they may be made of
polymers, of organic-silicon polymers, for example.

[0079] To implement the method with approaching the gas compression or
expansion processes closer to the isothermal ones, the means of gas
heating and cooling include at least one gas circulating pump
(hereinafter referred to as a gas blower for brevity) with the
possibility of creation forced gas convection in the gas reservoir of at
least one accumulator.

[0080] To improve isothermality the gas reservoir of at least one
accumulator communicates with the means of gas heating and cooling by at
least two gas lines with the possibility of gas removal by the gas blower
from said gas reservoir via one of said gas lines, transfer of the
removed gas through at least one heat exchanger and return of the gas to
the same gas reservoir through the other gas line.

[0081] In the embodiment of the device preferable in terms of simplicity
and reliability and containing a gas blower the means for supply and
intake of liquid include at least one hydromotor kinematicaly connected
with at least one gas blower, while the hydromotor is installed with the
possibility of being actuated by the flow of liquid between it and the
liquid reservoir of at least one accumulator.

[0082] To implement the method of conversion by cycle with heat
regeneration the device is proposed with at least one gas heat exchanger
embodied as a regenerating one, i.e. with the possibility of removing
heat from gas when the gas is pumped through it in one direction and of
supplying the heat removed from the gas to the gas when the gas is pumped
through it in the opposite direction.

[0083] The invention provides the use of heat of various sources. The
thermal contact of the hotter heat exchangers with them is effected
either by means of heat conductivity or heat-and-mass transfer, including
condensation heat transfer, or radiant heat transfer as well as their
combinations.

[0084] To ensure thermal contact with the heat source by means of
heat-and-mass transfer at least one heat exchanger has channels to pass
an external heat-transfer medium with the possibility of supplying heat
from this heat-transfer medium to the gas.

[0085] To increase efficiency when using a hot heat-transfer medium at
least one heat exchanger is made as a counterflow one, i.e. it has
channels to pass the external heat-transfer medium with the possibility
of supplying heat from this heat-transfer medium to the gas so that heat
is supplied to the gas entering the heat exchanger from the external
heat-transfer medium leaving the heat exchanger while heat to the gas
leaving the heat exchanger is supplied from the external heat-transfer
medium entering the heat exchanger. For said heat exchanger to be used as
a regenerating one, it has at least one additional port with the
possibility of introducing gas into the heat exchanger while the means of
heating and cooling contain at least one channel connecting the
additional gas port with the accumulator and are made with the
possibility of locking this channel.

[0086] To implement the method with creation of an inter-accumulator
liquid flow an embodiment of the device is proposed where the means for
supply and intake of liquid include means of inter-accumulator liquid
transfer embodied with the possibility of creating a liquid flow between
the liquid reservoirs of at least two accumulators so that the pressure
difference between any parts of the liquid in this flow does not exceed
30% of the pressure of the liquid in that liquid reservoir into which it
is pumped; preferably this difference does not exceed 5% of said
pressure.

[0087] Different embodiments of the means of inter-accumulator liquid
transfer are implied, with the use of both rotor and linear liquid pumps
and hydromotors as well as with the use of hydraulic transformers in
which the pump and motor are joined. In the latter case the means of
inter-accumulator liquid transfer include at least one hydraulic
transformer with at least three liquid ports installed with the
possibility of communicating via its two ports with the liquid reservoirs
of at least two accumulators and creating a liquid flow between them when
the liquid flows through at least its one other port. Provision is made
for use of various hydraulic transformers, for example, rotary
axial-piston hydraulic transformers with phase control (as in U.S. Pat.
No. 6,116,138) where every cylinder works as a motor during one part of
the revolution and as a pump during the other part, or multi-chamber
linear hydraulic transformers with digital control (as in U.S. Pat. No.
7,475,538). In a more compact embodiment at least one accumulator
combines the functions of a hydropneumatic accumulator and a hydraulic
transformer as in U.S. Pat. No. 5,971,027. Such an accumulator includes
at least two liquid reservoirs separated by one common piston separator
from one gas reservoir while the means of inter-accumulator liquid
transfer are made with the possibility of creating a liquid flow between
at least one of the liquid reservoirs of this accumulator and at least
one liquid reservoir of another accumulator.

[0088] To implement the method of conversion with transfer of liquid from
the line with the first high pressure to the line with the second high
pressure the means for supply and intake of liquid contain the first and
second lines with the possibility of maintaining the first and second
pressures, respectively, in them as well as the hydraulic transformer
with at least three ports installed with the possibility of liquid
exchange between said lines and the liquid reservoir of at least one
accumulator at the pressure in this liquid reservoir different from said
pressures in the lines.

[0089] To implement the method with the load pressure decoupling from said
pressures in the lines the means for supply and intake of liquid include
the hydraulic transformer with at least four ports installed with the
possibility of connecting two ports with said first and second lines and
connecting two other ports with two output lines and maintaining the
pressures in the output lines different from said pressures in the first
and second lines.

[0090] The details of the invention are shown in the examples given below
illustrated by the drawings and graphs presenting:

[0091]FIG. 1--The device with two accumulators and two heat exchangers

[0092]FIG. 2--The device with three accumulators, the gas blower, the gas
regenerating heat exchanger, liquid heat exchangers and the liquid heat
insulating buffer as well as with hydraulic transformers.

[0099] The primary principle of the proposed invention is illustrated in
FIG. 1. Improvements of the primary principle are illustrated in FIG. 2.
FIG. 3-FIG. 8 show particular embodiments of the main elements and parts.

[0100] The device according to FIG. 1 includes two hydropneumatic
accumulators 1 and 2, which liquid reservoirs 3 and 4 communicate with
the means for supply and intake of liquid 14. The liquid reservoirs 3 and
4 are separated by movable separators 5 and 6 from the gas reservoirs 7
and 8 communicating with the means of heating and cooling 9. For gas
heating and cooling these means contain flow gas heat exchangers 10 and
11 connected with the gas reservoirs 7 and 8 and accumulators 1 and 2 via
gas lines 12 and valves 13. The heat exchanger 10 is made with the
possibility of a thermal contact with an external heat source and with
the possibility of supplying heat to the gas from it. The heat exchanger
11 is made with the possibility of a thermal contact with the cooling
heat transfer medium and with the possibility of removing heat to it from
the gas.

[0101] The invention provides for use of heat of various sources,
including internal or external combustion engines, high-temperature fuel
cells, the sun, geothermal sources, etc. as well as direct heat of
exothermic reactions conducted in a thermal contact with the hotter heat
exchanger. The thermal contact with the heat source is effected either by
means of heat conductivity or heat-and-mass transfer using a hot
heat-transfer medium, for example, exhaust gases of an ICE (internal
combustion engine) or exhaust steam of a steam turbine, or radiant heat
transfer as well as their combinations. Provision is also made for
heat-and-mass transfer with condensation heat transfer, for example,
during recovery of the heat of exhaust steam of a steam turbine or in use
of heat pipes.

[0102] FIG. 3 shows the embodiment of the gas heat exchanger 10 (or 11),
the thermal contact with it being effected by means of heat and mass
transfer. It contains internal slot-type gas channels 15 radially
diverging from the internal axial channel 16, which greater part is
blocked by the plug 18 except for the collector parts 17. Gas input and
output are effected via the ports 19 in the flanges 20 (the second flange
is not shown). It is preferred that the aggregate gas volume in the
internal channels 15, 16 of the heat exchangers 10, 11 should not exceed
10% of the maximum aggregate gas volume in the gas reservoirs 7, 8 of the
accumulators. For heat supply from an external source the heat exchanger
according to FIG. 3 contains spiral external channels 21 through which
the heating heat-transfer medium circulating between the heat exchanger
10 and external heat source is pumped via external ports (not shown in
the figure). It is preferred that the heat exchanger 10 should be made
and installed as a counterflow one with the possibility of supply heat
from the heating heat-transfer medium to the gas so that the heat is
supplied to the gas entering the heat exchanger 10 from the external
heat-transfer medium leaving the heat exchanger 10 while the heat to the
gas leaving the heat exchanger 10 is supplied from the external
heat-transfer medium entering the heat exchanger 10. Thus, both fuller
use of the heat of the external source and higher gas heating are
achieved simultaneously. The heat exchanger with the cooling
heat-transfer medium pumped through its external channels is embodied and
installed in a similar way.

[0103] The gas heat exchanger 10 is heated from the external heat source
and becomes hotter. The gas heat exchanger 11 is cooled by the cooling
heat-transfer medium and becomes colder.

[0104] For conversion of the heat of an external source into fluid power
gas compression and expansion are combined with heat supply and removal
so that the average gas temperature during expansion is higher than
during compression. Compression and expansion hereinafter implies change
of the gas density (increasing or decreasing of the density,
respectively) due to the change of the gas reservoir volume in at least
one accumulator.

[0105] The device according to FIG. 1 can be used for the conversion heat
into fluid power with performance of the cycles combining isobaric,
isochoric and close to adiabatic polytrophic stages, for example, those
of Otto, Brayton, Diesel or other cycles. Hereinafter the real processes
in the gas cycle are approximately described by idealized stages (such as
adiabatic, isothermal, isobaric or isochoric).

[0106] Gas density changing (by gas expansion or compression) without gas
transfer through the heat exchanger implements polytropic expansion or
compression that approaches the adiabatic one at increased rate of
expansion or compression.

[0107] Gas transfer through the heat exchanger (hotter 10 or colder 11)
without gas density change, (that is with equal rates of gas displacement
from one accumulator and gas intake into another accumulator) implements
isochoric change of the gas temperature (heating or cooling,
respectively).

[0108] Gas transfer from one accumulator to another with expansion (that
is with increase of the aggregate volume of the gas reservoirs 7 and 8)
through the hotter heat exchanger 10 implements gas expansion with
heating, isobaric for example. The similar way gas compression (isobaric
for example) with cooling is implemented at gas transfer from one
accumulator to another with compression through the colder heat exchanger
11.

[0109] The proposed method of heat conversion into fluid power is not
limited to the cycles with the aforesaid idealized stages and applies to
all cycles in which gas expansion work exceeds gas compression work.

[0110] The example of the conversion heat into fluid power cycle, which is
implemented in the device embodiment according to FIG. 1, includes four
stages: the first stage of the polytropic gas compression in the gas
reservoir of the first accumulator; the second stage of the heat supply
to the gas and gas heating during gas transferring to another accumulator
through the hotter heat exchanger 10; the third stage of the polytropic
gas expansion in the gas reservoir of another accumulator and the fourth
stage of the heat removal from the gas and gas cooling during gas
transferring backward to the first accumulator through the colder heat
exchanger 11. At the beginning of the first stage gas is displaced from
the gas reservoir 8 of the accumulator 2 through the colder heat
exchanger 11 into the gas reservoir 7 of the accumulator 1 in the maximal
extent. As a result the initial gas temperature is close to the
temperature of the colder heat exchanger 11. Pumping working fluid by
means for supply and intake of liquid 14 into the liquid reservoir 3 of
the accumulator 1 the polytropic gas compression is being performed in
the gas reservoir 7 with the increase of gas pressure and temperature.
The polytropic gas compression is finished at the gas temperature less
than temperature of the hotter heat exchanger 10. During the second stage
the heat is being supplied to the compressed gas by transferring the gas
via valve 13 and hotter heat exchanger 10 from the gas reservoir 7 into
the gas reservoir 8 with pumping working liquid into the liquid reservoir
3 and displacement of working liquid from the liquid reservoir 4. The
supply of heat is performed with heating and expansion of the gas, i.e.
with the increase of the aggregate gas volume in the gas reservoirs 7 and
8. The amount of the working fluid being displaced from the liquid
reservoir 4 of the accumulator 2 into the means for supply and intake of
liquid 14 is greater than that being pumped from these means into the
liquid reservoir 3 of the accumulator 1. Preferably the gas transferring
is performed until maximal displacement of the gas from the gas reservoir
7 of the accumulator 1. At the third stage further gas expansion is
performed in the gas reservoir 8 of the accumulator 2 with the liquid
displacement from its liquid reservoir 4 into the means for supply and
intake of liquid 14. At this time the pressure and the temperature of the
gas decrease. The polytropic gas expansion is finished at the gas
temperature higher than the temperature of the hotter heat exchanger 10.
During the fourth stage the heat is being removed from the expanded gas
by transferring the gas via colder heat exchanger 11 and valve 13 from
the gas reservoir 8 into the gas reservoir 7 with pumping working liquid
into the liquid reservoir 4 and displacement of working liquid from the
liquid reservoir 3. The removal of heat is performed with cooling and
compression of the gas, i.e. with the decrease of the aggregate gas
volume in the gas reservoirs 8 and 7. The amount of the working fluid
being displaced from the liquid reservoir 3 of the accumulator 1 into the
means for supply and intake of liquid 14 is less than that being pumped
from these means into the liquid reservoir 4 of the accumulator 2. The
average temperature and the average pressure of the gas during expansion
at the second and third stages are higher than during compression at the
first and fourth stages. Therefore, the gas expansion work exceeds the
gas compression work. During the second and third stages the means for
supply and intake liquid 14 get more fluid power with the liquid
displaced from the accumulators than spend for the pumping of the working
fluid into the accumulators during the first and fourth stages. As a
result, some part of the heat is converted into additional fluid power
that is used by means for supply and intake of liquid 14 for mechanical
work in loads, in hydromotors or hydraulic cylinders, for example.
Various embodiments of the means for supply and intake of liquid 14 are
implied including both separate pumps and hydromotors and hydraulic
transformers.

[0111] The above-described primary principle of the invention is
implemented with higher efficiency using the improvements included in the
device embodiment according to FIG. 2.

[0112] In the device according to FIG. 2 the means of heating and cooling
9 contain check valves 22 installed so that gas is transferred through
the colder heat exchanger 11 only into the gas reservoir 7 of the
accumulator 1 and thus the walls of the gas reservoir 7 are maintained
colder. The hotter heat exchanger 10 is installed so that gas is
transferred through it from the gas reservoir 7 into the gas reservoir 8
and from it--into the gas reservoir 23 of the third accumulator 24 thus
maintaining the walls of the gas reservoirs 8 and 23 hotter.

[0113] In other embodiments with three and more accumulators the means of
heating and cooling can be made with the possibility of maintaining the
walls of the gas reservoirs of at least two accumulators colder and
transferring gas between them through the colder gas heat exchanger.

[0114] The means of heating and cooling 9 also contain liquid flow heat
exchanger 25 and check valves 26. The heat exchanger 25 is heated by heat
from an external heat source, by means of a hot heat-transfer medium, for
example. The working liquid directed into the liquid reservoir 4 of the
accumulator 2 or into the liquid reservoirs 27, 28 of the accumulator 24
is passed through the heated liquid heat exchanger 25 maintaining the
walls of said liquid reservoirs and the working liquid in them hotter. At
that the walls of the liquid reservoir 3 of the accumulator 1 and the
liquid in it remain colder. Thus the accumulators 2 and 24 are maintained
hotter in whole, whereas whole accumulator 1 is maintained colder.

[0115] Other embodiments can implement a cooling liquid heat exchanger
through which the working liquid is transferred at pumping to the liquid
reservoir of the accumulator with colder walls of the gas reservoir
(accumulator 1 in FIG. 1, FIG. 2 for example). Other embodiments can also
implement accumulators provided with heat exchangers for direct heating
or cooling of the accumulator walls.

[0116] In the device according to FIG. 2 the means for supply and intake
of liquid 14 include the liquid regenerating heat exchanger 29 and
heat-insulating buffer 30. In other embodiments only a liquid
regenerating heat exchanger or only a heat-insulating buffer can be used.
The liquid regenerating heat exchanger 29 is connected with liquid
reservoirs 4, 27 and 28 of both hot accumulators with the possibility of
removing heat from the liquid during its displacement through it from
these accumulators into the heat-insulating buffer 30 and supplying the
removed heat to the liquid during reverse transfer of the liquid from the
buffer 30 into these accumulators. The working liquid directed from the
hot accumulators 2 or 24 through the heat exchanger 29 is cooled
transferring the heat from the liquid to the heat exchanger 29. The
working liquid directed into the hot accumulators 2 or 24 through the
same heat exchanger 29 in the reverse direction is heated transferring
the heat from the heat exchanger 29 to the liquid. Thus, the temperature
of the working liquid directed to the heat-insulating liquid buffer 30
including two liquid reservoirs of variable volume 31 and 32 and
separated by a movable heat insulator 33 is reduced. The use of
high-temperature working liquid (for example, organic or organic-silicon
one) allows to raise its temperature to 300 C and higher.

[0117] For the use of different working liquids in the cold and hot
accumulators it is possible to apply a separate liquid buffer including
two variable-volume reservoirs separated by a movable separator. Or the
liquid buffer 30 can be made with a liquid-tight movable heat-insulating
separator 33.

[0118] Various embodiments of the liquid regenerating heat exchanger 29
are proposed including regenerating elements installed inside a strong
shell as well as those made in the form of a single element with high
thermal capacity and low heat transfer from its hotter part to the colder
part (for example, in the form of a long pipe). In the integrated
embodiment according to FIG. 4 the liquid regenerating heat exchanger 29
and the liquid heat-insulating buffer 30 according to FIG. 4 are embodied
in a common outer strong shell 34 with liquid ports 35 and 36 on its
flanges. Inside the strong shell 34 there is a thin-walled metal sleeve
37 with a movable heat insulator 33 with the sliding possibility
installed in it in the form of a long hollow piston 38 separating the
high-temperature and low-temperature variable-volume reservoirs 31 and
32. In the space 39 between the strong shell 34 and the metal sleeve 37
the filler 40 is placed (for example, mineral wool or foamed polymer)
preventing convection of the high-temperature liquid with low heat
conductivity filling that space. The cavity 41 inside the hollow piston
38 also contains the filler 40 and high-temperature liquid with low heat
conductivity. In this case this liquid is the working liquid filled
through the holes 42 in the sleeve 37 and the holes 43 in the walls of
the hollow piston 38. This liquid provides hydrostatic unloading of the
thin sleeve 37 and thin walls of the piston 38. In other embodiments it
is possible to use a solid heat-protective insert made of a
high-temperature material with low heat conductivity (preferably less
than 1 W/(m*K), for example, made of high-temperature plastic
(polyimide-like for example), instead of the thin-walled metal sleeve 37
and the layer of a heat-protective liquid separated by it along the
strong shell 34. The movable heat-insulator 33 can be also made from a
similar solid material with low heat conductivity.

[0119] The high-temperature variable-volume reservoir 32 communicates with
the flow part 44 of the liquid regenerating heat exchanger 29 that is
filled with regenerating elements 45. In this case they are embodied in
the form of balls made of a high heat conductivity metal (aluminum, for
example). To reduce the dimensions the regenerating elements 45 may
contain materials undergoing phase transition during heat exchange with
the passing liquid (for example, melting during heat removal from the
liquid and crystallization during heat supply to the liquid).

[0120] In the embodiment according to FIG. 2 the gas heat exchanger 10 is
made as a separate element and installed between the accumulators 2 and
24 with the possibility of transferring gas through it from the smaller
gas reservoir 8 of the accumulator 2 into the larger gas reservoir 23 of
the accumulator 24, thus approaching the gas expansion process closer to
the isothermal one. To ensure compactness and lower pressure losses
during gas transfer the embodiment according to FIG. 5 is proposed where
the gas heat exchanger 10 is made in the same housing with the
accumulator 2 as a gas port of this accumulator with increased area of
the heat exchanging surface. It contains external channels 21 for the
heating heat transfer medium, a strong shell 46 common with the
accumulator 2 as well as the inner heat exchanging section 47 made of a
high heat conductivity metal (preferably from copper or aluminum). In
this section internal slot-type gas channels 15 are made radially
diverging from the axial channel 16, with its greater part blocked by a
plug 18 except for the collector part 17. In the embodiment with two
hotter accumulators, as according to FIG. 2, gas is transferred through
this hotter heat exchanger 10 during transfer to the hotter accumulator 2
from the colder accumulator 1 and during transfer from the smaller hotter
accumulator 2 to the larger hotter accumulator 24.

[0121] Similarly, in other embodiments the colder gas heat exchanger 11
can be embodied in the same housing with the colder accumulator 1.

[0122] The means of heating and cooling 9 according to FIG. 2 include the
gas blower 48 installed with the possibility of creating forced
convection in the gas reservoir 7 of the colder accumulator 1. The gas
reservoir 7 communicates with the means of heating and cooling 9 via at
least two gas lines 49 and 50 with the possibility of gas removal by the
gas blower 48 from the gas reservoir 7 via the gas line 49, transfer of
the removed gas through the colder flow gas heat exchanger 11 and return
of the gas to the same gas reservoir 7 via the other gas line 50. In
other embodiments with an external heat exchanger the gas blower can be
placed in the housing of the accumulator and can create forced convection
without gas transfer through the external heat exchanger, thus
approaching gas compression or expansion closer to the isothermal process
only due to heat exchange with the walls of the gas reservoir.

[0123] The means for supply and intake of liquid 14 according to FIG. 2
include a hydromotor 51 kinematically connected with the gas blower 48 by
means of the shaft 52. In other embodiments kinematical connection of the
hydromotor with the gas blower may include a gear box for the gas blower
rotation speed increase). The hydromotor 51 is connected with the liquid
line 67 via valve 103 with the possibility of being actuated by the
liquid flow between it and the liquid reservoir 3 of the accumulator 1.

[0124] In the integrated embodiment according to FIG. 6 both the flow gas
heat exchanger 11 and the centrifugal gas blower 48 are embodied in the
same housing with the accumulator 1. The gas blower 48 is connected with
hydromotor 51 by means of the shaft 52. The check valves 22 (FIG. 2) are
not shown on the FIG. 6. One of these valves can be embodied as a
disc-valve installed at the face of the internal heat-exchanging section
47 with a possibility to lock the heat-exchanging slot channels 15.
Another check valve can be installed in the axial channel 16. This
integrated embodiment increases compactness and eliminates the need for
gas lines that reduces total gas dynamic resistance.

[0125] When working liquid is pumped into the liquid reservoir 3 of the
accumulator 1, it actuates the hydromotor 51 and the gas blower 48
kinematically connected with it. The centrifugal gas blower 48 (FIG. 6)
intakes the gas from the gas reservoir 7 via the axial channel 16 and
pumps it into the slot-type channels 15 of the heat exchanger 11 from
which the gas goes back into the gas reservoir 7 where forced convection
is created. The intensified heat exchange of the gas with the walls of
the gas reservoir 7 and the surfaces of the slot-type channels 15
approaches the gas compression process in this gas reservoir closer to
the isothermal one.

[0126] The liquid actuating the hydromotor 51 and the gas pumped by the
gas blower 48 have close pressures and close temperatures, which promotes
a favourable operating condition of the shaft 52 seals.

[0127] In other embodiments the gas blower can be installed with the
possibility of creating forced convection in the gas reservoir of the
hotter accumulator. Also in other embodiments the gas blower can be
kinematically connected with the electric motor located in the high
pressure cavity, preferably filled with liquid.

[0128] The device according to FIG. 2 includes a regenerating flow gas
heat exchanger 53 to which heat is removed from gas when gas is
transferred through it to the colder accumulator 1 and from which the
heat removed from the gas is supplied back to the gas when the gas is
transferred through it in the opposite direction, i.e. from the colder
accumulator 1 to the hotter accumulator 2. At that its part which the gas
enters from the colder accumulator 1 becomes colder while the opposite
part which the gas enters from the hotter accumulators 2 or 24 becomes
hotter. At the cooling stage heat from the gas is supplied to the
regenerating heat exchanger 53 and then to the cooling heat transfer
medium through the colder heat exchanger 11. At the heating stage heat is
supplied to the gas first from the regenerating heat exchanger 53 and
then from the external heat source through the hotter heat exchanger 10.

[0129] It is preferred that the aggregate gas volume in the regenerating
heat exchanger 53 should not exceed 10% of the maximum aggregate gas
volume in the gas reservoirs of the accumulators. The thermal capacity of
the regenerating heat exchanger 53 exceeds the maximum aggregate thermal
capacity of the gas (preferably not less than twice). The configuration
of the regenerating heat exchanger (length, longitudinal and cross
sections) and the heat conductivity of the material of the regenerating
heat exchanger have been chosen so that the heat transfer from its hotter
part to its colder part should be less than the heat transfer from the
gas to the cooling heat transfer medium in the colder heat exchanger 11
(preferably, less than 30% of said heat transfer). Various embodiments of
a regenerating heat exchanger 53 are proposed both including regenerating
elements installed inside the strong hermetically sealed shell as well as
embodied in the form of a single element with a small inner volume, high
thermal capacity and low heat transfer from the hotter part to the colder
part. In the particular embodiment according to FIG. 7 the regenerating
gas heat exchanger 53 includes a strong shell 54 with the heat-insulating
insert 55, with a regenerating element 56 placed inside it in the form of
a spiraled sheet 57 with gaskets 58 determining the gaps between the
layers of the spiral. Flowing through these gaps the gas exchanges heat
with the surfaces of the regenerating element getting colder or hotter
depending on the transfer direction. In this embodiment use is made of a
metal sheet (preferably, from a low heat conductivity metal, stainless
steel, for example). To reduce longitudinal heat conductivity the metal
sheet 57 has the perforation 59, breaking the regenerating element into
several sections with increased heat resistance between them in the zones
of perforation the 59. In other embodiments the regenerating elements can
be made from high-temperature plastics without perforation. The
heat-protective insert 55 made from a high-temperature plastic or
ceramics reduces heat losses of heating and cooling of the strong shell
54. In other embodiments it is possible to use a layer of heat-insulating
liquid instead of the heat-protective insert 55, the liquid being
separated from the gas part with the regenerating element by a thin metal
sleeve (similarly to the heat-protective layer of liquid in the liquid
regenerating heat exchanger 29 according to FIG. 4).

[0130] In other embodiments a part of the heat exchanger 10 (or 11) can be
used as a gas regenerating heat exchanger 53. For that purpose an
additional gas port is made in such a heat exchanger with the possibility
of introducing gas into the heat exchanger while the means of heating and
cooling contain at least one channel connecting the additional gas port
with the gas reservoir 23 (or the gas reservoir 7) and contain a valve
installed with the possibility of locking this channel.

[0131] Heat regeneration combined with approaching compression and
expansion closer to isothermal processes provides high thermodynamic
efficiency of heat conversion into the work performed by gas during
displacement of the liquid from the accumulators.

[0132] The means for supply and intake of liquid 14 according to FIG. 2
include hydraulic transformer 60 and the valves 61, 62 and 63 that
together with liquid lines 64-67 form the means of inter-accumulator
liquid transfer made with the possibility of creating a liquid flow
between the liquid reservoirs of the accumulators 1, 2 and 24.

[0133] The hydraulic transformer 60 has three liquid ports 68, 69 and 70.
The port 68 is connected via the valves 63 and 103 with the liquid
reservoir 3 of the accumulator 1, while the port 69 is connected through
the valves 62, 26 and 63, liquid heat-insulating buffer 30 and the
regenerating liquid heat exchanger 29 with the liquid reservoir 4 of the
accumulator 2 or with the liquid reservoirs 27 and 28 of the accumulator
24. The third port 70 of the hydraulic transformer 60 is connected with
the liquid line 71. When liquid flows through this third port 70, the
liquid flow is created between the ports 68 and 69 of the hydraulic
transformer 60 and, accordingly, between the liquid reservoirs of the
accumulators with which these ports communicate.

[0134] The accumulator 24 according to FIG. 2 is embodied like in U.S.
Pat. No. 5,971,027 and combines the functions of a hydropneumatic
accumulator and a hydraulic transformer. It has 3 ports (the gas port 72
and the liquid ports 73 and 74) and includes two liquid reservoirs 27 and
28 separated by one common piston separator 75 from one gas reservoir 23.
The means of inter-accumulator liquid transfer include valve 61 and the
lines 64 and 65 for creation of a liquid flow between the liquid
reservoir 27 of the accumulator 24 and the liquid reservoir 4 of the
accumulator 2. The liquid reservoirs 27 and 28 are separated one from
another, which allows maintaining different pressures in them so that the
aggregate force of pressure of the liquid on the separator 75 balances
the force of gas pressure on it. When gas is transferred from the gas
reservoir 8 of the accumulator 2 into the gas reservoir 23 a counter-flow
of liquid is created into the liquid reservoir 4 of the accumulator 2
from the liquid reservoir 27, maintaining the pressure in it higher than
that in the gas reservoir 23. At that the pressure in the other liquid
reservoir 28 connected with the hydraulic transformer 76 via the valve 62
(and via regenerating heat exchanger 29 and heat insulating buffer 30) is
maintained at a lower level than in the gas reservoir 23. By varying the
ratio between the flow rates through the ports 77, 78 and 79 of the
hydraulic transformer 76 the pressure of the liquid flowing through its
port 77, connected with the liquid reservoir 28, is varied. Thus by means
of the hydraulic transformer 76 the pressure in the liquid reservoir 28
is maintained lower relative to the gas pressure in the gas reservoir 23.
Due to aforesaid balance of the forces acting upon the separator 75 the
pressure in the liquid reservoir 27 becomes increased relative to the gas
pressure in the gas reservoir 23. At steady rate of mutual gas and liquid
transfer between the accumulators 2 and 24 the value of this relative
excess of the liquid pressure in the liquid reservoir 27 over gas
pressure in the gas reservoir 23 corresponds to the value of the
aggregate pressure drop on the separators 75 and 6 caused by friction and
the pressure drop on the resistances of the gas-liquid circuit through
which gas transfer and liquid counter-transfer occur. This circuit
includes gas and liquid ports of the accumulators 1, 2 and 24, gas heat
exchanger 10, as well as valves and lines. Since the pressure drop on
said circuit increases with the increase of the rate of mutual gas and
liquid transfer between the accumulators 2 and 24 for the transfer rate
increase said value of the pressure excess in the liquid reservoir 27
relative to the pressure in the gas reservoir 23 is increased and it is
decreased for the transfer rate decrease.

[0135] In other embodiments such an accumulator with several liquid
reservoirs can be used as the second colder accumulator (or as the only
hotter accumulator, for example, instead of the accumulator 2 according
to FIG. 1). In this case during the back transfer of gas from it into the
smaller accumulator (for example, into the accumulator 1 according to
FIG. 1) a counterflow of liquid is created from the liquid reservoir of
the smaller accumulator to one (or several) liquid reservoir of such an
accumulator maintaining pressure in it lower than the gas pressure. At
that the pressure in another liquid reservoir (or several other liquid
reservoirs) of this accumulator is maintained higher than the gas
pressure in its gas reservoir, by means of the hydraulic transformer as
well, for example. Such an integrated accumulator embodiment with two
liquid reservoirs combining the functions of accumulator and hydraulic
transformer reduces inter-accumulator liquid transfer losses and improves
the device compactness. In other integrated embodiments the accumulators
can contain several liquid reservoirs as well as several gas reservoirs
in one housing. From the perspective of the present invention the number
of the accumulators in such integrated embodiments is equal to the number
of independently moving separators between the gas and liquid reservoirs.

[0136] The hydraulic transformer 60 and valves 62, 63 are used for
creating the liquid flow between the accumulator 2 and the accumulator 1
during gas transfer between them with heat supply from the regenerating
heat exchanger 53 and hotter heat exchanger 10 as well as for creating
the liquid flow between the liquid reservoirs 27, 28 of the accumulator
24 and liquid reservoir 3 of the accumulator 1 during gas transfer
between the accumulators 24 and 1 with heat removal from gas to the
regenerating heat exchanger 53 and colder heat exchanger 11. During gas
transfer from the gas reservoir 7 to the gas reservoir 8 the liquid
reservoir 3 is connected to the port 68 (via valves 103, 63) while the
liquid reservoir 4 is connected to the port 69 (via valves 61, 26, 62,
liquid regenerating heat exchanger 29 and liquid heat-insulating buffer
30). Maintaining (by means of hydraulic transformer 60) the pressure of
the liquid in the liquid reservoir 3 at a higher value than the gas
pressure in the gas reservoir 7, gas is displaced from the accumulator 1
to the accumulator 2 and a counterflow of liquid is created between the
accumulators 2 and 1 through the ports 68, 69 of the hydraulic
transformer 60 with the displacement of the differential flow of the
liquid through its third port 70, line 71 and check valve 97 to line 90.

[0137] When gas is transferred from the gas reservoir 23 into the gas
reservoir 7 of the accumulator 1 both liquid reservoirs 27 and 28 are
connected with the port 69 of the hydraulic transformer 60 (via valves
61, 62 and the liquid regenerating heat exchanger 29 and the liquid
heat-insulating buffer 30). With the hydraulic transformer 60 maintaining
the liquid pressure in these liquid reservoirs at a higher value than the
gas pressure in the gas reservoir 23, gas is displaced from the
accumulator 24 to the accumulator 1 and a counterflow of liquid is
created into the liquid reservoirs 27 and 28 from the liquid reservoir 3
of the accumulator 1 through the ports 68, 69 of the hydraulic
transformer 60 with the delivery of the differential flow of the liquid
through its third port 70, line 71 and check valve 97 from line 89. Thus,
in both cases the hydraulic transformer 60 allows to overpower the
aggregate pressure drop on resistances of the gas-liquid circuit
including the gas and liquid ports of the accumulators 1, 2, 24, gas and
liquid heat exchangers, liquid buffer, valves and lines, and, in
addition, the pressure drop on separators caused by friction.

[0138] In the embodiment according to FIG. 2 the hydraulic transformer 60
is made as a variable one with the possibility of varying ratios between
liquid flow rates through its ports 68, 69, 70 and thereafter with the
possibility of maintaining different ratios between the pressures of
liquid in these flows. In other embodiments the hydraulic transformer 60,
that is used for the inter-accumulator transfer of liquid, can be made as
a non-adjustable one, i.e. with constant ratio between liquid flow rates
through its ports, for instance comprising three liquid reservoirs
separated by one separator like accumulator 24. FIG. 8 shows an
integrated embodiment of such hydraulic transformer combined with the
heat-insulating liquid buffer. Two its liquid reservoirs 80 and 81 are
separated by one common heat-insulating piston separator 82 from a larger
liquid reservoir 83. The heat-insulating piston separator 82 slides along
a heat-insulating insert 84 installed inside a strong shell 85. During
inter-accumulator transfer of gas and liquid the reservoirs 81 and 83 are
used for the liquid exchange with the liquid reservoirs of the
accumulators between which the liquid is being transferred. The larger
reservoir 83 is connected to the hotter accumulator (e.g. to the
accumulator 2 or 24, FIG. 2) and exchanges hotter liquid with it. The
smaller reservoir 81 is connected to the colder accumulator (e.g. to the
accumulator 1, FIG. 2) and exchanges colder liquid with it. A ratio of
the cross-section areas of the reservoirs 83 and 81 is equal to the
extent of the gas volume change at the stages of the gas transfer between
the colder and the hotter accumulators through heat exchangers. The
cross-section area of the third reservoir 80 is equal to the difference
between cross-section areas of the reservoirs 83 and 81. Thereafter the
liquid flow through the liquid port 86 is equal to the difference between
the flows through the port 88 and port 87. The third reservoir 80 is used
for the intake of the differential liquid flow during the gas
transferring with the compression and for the displacement of the
differential liquid flow during the gas transferring with the expansion.
These heat-insulating piston separator 82 and insert 84 are made of
heat-insulating materials (e.g. polyimide or another high-temperature
plastics) which reduces the heat transfer through them between the hotter
liquid in the reservoir 83 and the colder liquid in the reservoirs 80 and
81. A long sliding contact between the piston separator 82 and the insert
84 reduces heat losses on the cyclic heating and cooling of the part of
the surface of the heat-insulating insert 84 that contacts to the hotter
liquid in the reservoir 83. For the using of such integrated embodiment
as a heat-insulating buffer only both smaller liquid reservoirs 80 and 81
are interconnected. Such integrated embodiment results in the reduction
of the total hydrodynamic resistance and better compactness of the
device.

[0139] In all the described cases of creation of the inter-accumulator
liquid flow the rate of mutual exchange of gas and liquid between
accumulators is changed by changing the pressure excess in the liquid
reservoir of the respective accumulator over the gas pressure in the gas
reservoir of the same accumulator for instance by regulating the
respective hydraulic transformer or other hydromechanical means. Said
rate can be changed by changing the extent of the gas temperature change
during its transfer (for instance by changing the temperature of the heat
exchangers 10 or 11) as well. The flow rate of the inter-accumulator
liquid flow is chosen so as the pressure difference between any parts of
the liquid in it (caused by the resistance of the aforementioned circuits
and friction of the seals of the hydraulic transformers) does not exceed
several bar, preferably does not exceed 1 bar. As the working pressures
of the gas and liquid in the accumulators are dozens and hundreds bar,
the pressure difference between any parts of the liquid in this flow does
not exceed 30% of the liquid pressure in the liquid reservoir in which it
is pumped to, preferably this difference does not exceed 5% of said
pressure.

[0140] The means for supply and intake of liquid according to FIG. 3
contain the first line 89 and second line 90 equipped with accumulators
91 and 92 as well as a replenishment pump 93 with valves 94 and 95 with
the possibility maintaining different pressures in these lines (in line
89--the first pressure changing in the first assigned range and in line
90--the second pressure changing in the second assigned range) as well as
hydraulic transformer 76 with three ports 77, 78 and 80. Two of the ports
78 and 79 are connected to lines 89 and 90. The third port 77 is
connected via valves 63, 62 and 61 with the liquid reservoir 3 of the
accumulator 1 and with liquid reservoirs 27 and 28 of the accumulator 24.
The hydraulic transformer 76 is embodied as a variable one with the
possibility of varying (continuously or stepwise) ratio between liquid
flow rates through its ports and thereafter ratio between pressures in
these ports. Thus, at the stages with gas pressure changing the hydraulic
transformer 76 ensures the possibility of liquid exchange between the two
said lines 89, 90 and the said liquid reservoirs of accumulators 1, 2 or
24 at pressures different from the given first and second pressures in
the lines 89, 90.

[0141] Both the first and second pressures in the lines 89, 90 are
maintained at a high value (preferably, dozens or hundreds bar), with the
second pressure being higher than the first one. To stabilize the
pressure in the lines 89, 90 use is made of accumulators 91, 92 with
larger working volumes than the aggregate working volume of the
accumulators 1, 2 and 24. When the device is brought to its initial
state, the replenishment pump 93 delivers liquid via the valves 94, 95
from the tank 96 into the accumulators 91, 92 until pressure is set in
the first and second lines 89, 90 within the assigned first and second
ranges, respectively.

[0142] Conversion is conducted as a cycle including the stage of gas
compression in the accumulator 1 with the colder gas reservoir 7, the
stage of gas transfer from it through the hotter heat exchanger 10 into
the accumulator 2, the stage of gas transfer from the accumulator 2 into
the accumulator 24 with gas expansion in their hotter gas reservoirs 8
and 23 as well as the stage of gas transfer from the accumulator 24
through the colder heat exchanger 11 into the accumulator 1.

[0143] Gas is compressed in the accumulator 1 from the pressure below the
pressure in the line 89 to the pressure above the pressure in the line 90
by pumping working liquid into its liquid reservoir 3 by means of the
hydraulic transformer 76 actuated by the liquid flow through its port 79
from the line 90. During the gas compression the liquid pressure in the
liquid reservoir 3 of the accumulator 1 is being raised by regulating of
the hydraulic transformer 76, namely by raising the ratio of the flow
rate of the liquid delivered into the hydraulic transformer 76 via port
79 from line 90 to the flow rate of the liquid displaced from it via port
77 to the accumulator 1. The hydromotor 51 actuates the gas blower 48
that pumps gas through the heat exchanger 11, which results in heat
removal from the gas and brings the gas compression process closer to the
isothermal one.

[0144] After the liquid pressure in the liquid reservoir 3 has been raised
up to the pressure above the second pressure (in the second line 90) the
valves 62 and 63 are switched over to the stage of the gas transfer from
the accumulator 1 into the accumulator 2 at the working liquid pressure
in the accumulators exceeding the second pressure. The working liquid
flow from the liquid reservoir 4 of the accumulator 2 to the line 90
actuates the hydraulic transformer 60 that creates the working liquid
flow from the accumulator 2 to the accumulator 1. As a result gas is
displaced from the gas reservoir 7 into the gas reservoir 8. In this case
gas is transferred through the check valve 22, regenerating gas heat
exchanger 53 and the hotter heat exchanger 10. Due to supply of heat to
the gas from the regenerating heat exchanger 53 and the hotter heat
exchanger 10 the gas heating goes on and expansion approaches the
isobaric process.

[0145] Gas is expanded in the accumulators 2, 24 with hotter gas
reservoirs 8, 23 from the pressure exceeding that in the line 90 to the
pressure below the pressure in the first line 89 by displacing the
working liquid from the liquid reservoir 28 to the line 89 through the
hydraulic transformer 76 actuating it and creating the working liquid
flow from it to the line 90. During the gas expansion the liquid pressure
in the liquid reservoirs 28, 27, 4 of the accumulator 24 and 2 is being
reduced by regulating of the hydraulic transformer 76, namely by raising
the ratio of the flow rate of the liquid delivered into the hydraulic
transformer 76 via port 77 from to the liquid reservoir 28 of the
accumulator 24 to the flow rate of liquid displaced from it via the port
79 to the line 90. The pressure of the liquid flowing through the port 77
of the hydraulic transformer 76 from the liquid reservoir 28 is being
maintained lower than the gas pressure in the gas reservoir 23. At the
same time the other liquid reservoir 27 of the same accumulator 24
creates the pressure that is higher than the gas pressure while the
liquid from the liquid reservoir 27 of the accumulator 24 is being
transferred to the liquid reservoir 4 of the accumulator 2. The heat
supply to the gas during gas transfer through the heat exchanger 10
brings the gas expansion process closer to the isothermal one.

[0146] After the liquid pressure in the liquid reservoir 3 has been
reduced down to the pressure below the first pressure (in the first line
89) the valves 61, 62 and 63 are switched over to the stage of the gas
transfer from the accumulator 24 with the hotter gas reservoir 23 into
the accumulator 1 with the colder gas reservoir 7 which is conducted at
the working liquid pressure in the accumulators below the first pressure.
The working liquid flow from the line 89 (via respective check valve 97)
to the liquid reservoirs 27, 28 of the accumulator 24 actuates the
hydraulic transformer 60 that creates the working liquid flow from the
accumulator 1 to the accumulator 24; hence, gas is displaced from the gas
reservoir 23 into the gas reservoir 7. In this case gas is transferred
through the regenerating gas heat exchanger 53, colder heat exchanger 11
and respective check valve 22. Due to heat removal from the gas to the
regenerating heat exchanger 53 and colder heat exchanger 11 the gas is
cooled and compressed, the process approaching the isobaric one.

[0147] As a result of every conversion cycle some part of the working
liquid is transferred from the line 89 with the first pressure to the
line 90 with the second, higher pressure. The approach of the compression
and expansion to the isothermal processes and the gas heat regeneration
between the stages of isobaric compression and expansion bring the gas
cycle close to the Ericsson cycle of the second type (two isotherms and
two isobars with heat regeneration between the isobars). The closer the
gas compression and expansion to the isotherm and the closer the heat
regeneration rate to 100%, the closer the thermodynamic efficiency of
such a cycle to the thermodynamic limit, i.e. to the Carnot cycle
efficiency.

[0148] The sliding seals of hydraulic transformers 60 and 76 (as well as
the seals of the separator 75 of the accumulator 24) operate at
differential pressures rather than at full ones, which reduce losses on
leakages and friction and increase the hydromechanical efficiency of the
conversion.

[0149] The means for supply and intake of liquid 14 according to FIG. 2
also include a hydraulic transformer 98 with four ports 99, 100, 101,
102. Two ports 99 and 100 are connected with the said first and second
lines 89, 90 while the other two ports 101 and 102 are connected with two
output lines 104 and 105. The hydraulic transformer 98 is embodied as a
regulated one with the possibility of maintaining pressures in the output
lines 104, 105 different from the pressures in the first and second lines
89, 90. The process of the above-described cyclic heat conversion into
fluid power involves alternating stages with supply of the liquid from
the first and second lines 89, 90 to the accumulators 1, 24 and intake of
the liquid into the said lines 89, 90 from the accumulators 2, 24.
Therefore, the pressure in these lines is subject to cyclic changes in
the assigned first and second pressure ranges. Control of the pressure
transformation rate in the hydraulic transformer ensures independence of
the power transferred to the load 106 from these cyclic pressure
fluctuations. When the first or second pressure goes beyond the assigned
ranges due to leakages in the hydraulic transformer 76 or 98, these
pressures are restored by means of a replenishment pump 93 and valves 94
and 95. Thus, the pressures are isolated optimizing the efficiency of the
gas cycle by the choice of the given first and second pressures in the
lines 89, 90 and optimizing the load 106 conditions by the choice of the
high and low output pressures in the lines 104, 105.

[0150] As a result the heat transferred with small losses from the heat
source to gas is converted with high thermodynamic efficiency into gas
work that is transformed with high hydromechanical efficiency into fluid
power transferred to the load.

[0151] Thus, the proposed method of heat conversion into fluid power and
the device for its implementation provide: [0152] high rate of heat use
due to inter-accumulator gas transfer through heat exchangers that
eliminates heat losses of cyclic heating and cooling of massive elements,
especially combined with elimination of gas heat losses at heat exchange
with the walls of the accumulator as well as elimination of gas heat
losses at heat exchange with liquids by preservation or regeneration of
the working liquid heat; [0153] high thermodynamic efficiency of the gas
cycle converting the heat supplied to the gas into work performed by the
gas, especially combined with gas heat regeneration and in combination
with gas compression or expansion processes approaching the isothermal
ones; [0154] high hydromechanical efficiency of gas work conversion into
fluid power due to inter-accumulator liquid transfer with small pressure
differences by means of hydraulic transformers, especially in combination
with isobaric exchange of liquid between the accumulators and lines at
small pressure differences as well as in combination with the use of
hydraulic transformers for liquid supply or intake at gas compression or
expansion, respectively; [0155] high general efficiency of heat
conversion into fluid power transferred to the load due to combination of
the aforesaid factors, especially in combination with the use of the
hydraulic transformer ensuring pressure transformation in the lines
exchanging liquid with the accumulators into the pressures in the lines
exchanging liquid with the load; [0156] high power density due to high
gas and liquid pressures and high transformation efficiency; [0157]
increased reliability due to elimination of cyclic heating and cooling of
the elements under high pressure; [0158] possibility of accumulating heat
in massive heat exchangers and using it for its conversion into fluid
power during temporary shutdown or reduction of the heat source power.

[0159] Specialists understand that this detailed description is given as
an example and many other variants within the limits of this invention
may be proposed, including, for example, (but not limited to)
implementations of the method that have not been described here in detail
and differ by the type of the gas cycle, choice of working liquids and
gases as well as the type of the external heat source and cooling heat
transfer medium and specific features of the thermal contact with it, as
well as embodiments of the device differing by the number and embodiments
of the accumulators, gas and liquid heat exchangers, gas blowers, means
for supply and intake of liquid, including hydraulic transformers and
buffers and other components of the device as well as variants of
integrated embodiments of the components of the device that were not
described above.

Patent applications in class Having means within the working chamber to effect the pressure of fluid therein

Patent applications in all subclasses Having means within the working chamber to effect the pressure of fluid therein